The present invention relates to a universal-serial-bus (xe2x80x9cUSBxe2x80x9d) hub circuit and a display device to which a plurality of computers can be connected.
In recent years, computers have been used in various applications. Some display devices such as those using CRT, LCD, or plasma are connectable to a plurality of computers. For example, a user who operates two computers assigns different jobs to respective computers. In this case, one display device is connected up to these two computers, and the user can select the computer through the display device. Among these smart display devices, some of them include a function for selecting an active computer by detecting signals from the computer.
A display device incorporating a USB hub circuit has drawn attention from the market, and a number of such display devices have increased recently. The USB hub circuit under the common standard with peripheral devices such as a mouse, keyboard and the like is defined as shown in FIG. 4. A USB hub circuit 31 has two types of connections, i.e. one is an upstream terminal 32 for connecting to a computer, and another is a plurality of downstream terminals 33 for USB devices. For instance, when a user connects a USB compatible computer 34 to a display device having a built-in USB hub circuit, the display device is coupled to the computer 34 via the upstream terminal 32. On the other hand, the USB compatible keyboard and mouse 35 are coupled to the display device via downstream terminals 33. This construction allows the keyboard and mouse to be connected directly to the display device that is placed just in front of the computer, i.e. at the user side. Further, this construction advantageously simplifies the connections because the same connecting terminals are used.
The display device incorporating the USB hub circuit 31, however, has the following inconveniences with all the advantages discussed above. Since the USB hub circuit 31 has only one upstream terminal 32, the computer must be re-connected via the upstream terminal 32 to the circuit 31 every time when the user changes the computer. The re-connection annoys the user and wastes time.
The present invention addresses the problem discussed above, and aims to provide a USB hub circuit and a display device. Through the circuit and device, a computer to be used can be selected with ease.
The USB hub circuit of the present invention comprises the following elements:
a switch circuit disposed between a plurality of upstream terminals to which respective computers are connected and a USB hub section; and
a selector for coupling the USB hub section with a selected upstream terminal determined by operating the switch circuit.
A first type display device of the present invention incorporates the above mentioned USB hub circuit.
This construction allows the display device to select a computer to be used only by switching the switch circuit through the selector. Re-wiring between the computer and the USB hub section can be thus advantageously eliminated.
A second type display device of the present invention comprises the following elements:
a first switch circuit disposed between a plurality of upstream terminals to which respective computers are connected and a USB hub section;
a second switch circuit disposed between a video display circuit and a plurality of video and sync. signal-input-terminals, and the same computer is connected to respective terminals; and
a selector for coupling the USB hub section with a selected upstream terminal as well as the display circuit with a selected video and sync. signal-input-terminal by operating the first and second switch circuits.
This construction allows the second type display device to select a computer to be used only by switching the first switch circuit. At the same time, it also allows the second type display device to switch the display screen proper to the computer to be used by the second switch circuit.
A third type display device of the present invention comprises the following elements:
a first switch circuit disposed between a plurality of upstream terminals to which respective computers are connected and a USB hub section;
a second switch circuit disposed between a video display circuit and a plurality of video and sync. signal-input-terminals, and the same computer is connected to respective terminals; and
a controller for identifying an active computer based on the sync. signal supplied through the second switch circuit, and for coupling the USB hub section with the upstream terminal connecting to the active computer by operating the first switch circuit.
This construction allows the third type display device to switch the display screen based on the sync. signal supplied from the active computer, and at the same time, it allows the first switch circuit to couple the active computer with the USB hub circuit.
As discussed above, the first type display device of the present invention allows the switch circuit employing the selector to change the computer. This first type display device thus eliminates the need to re-connect the computer to the USB hub section, and the computer to be used can be selected with ease.
The second type display device of the present invention also allows the first switch circuit employing the selector to change the computer with ease. At the same time, this second type display device allows the second switch circuit to select the display screen proper to the computer to be used.
The third type display device of the present invention selects the display screen based on the sync. signal fed from the active computer, and at the same time, allows the first switch circuit to couple the active computer to the USB hub section. As a result, this third display device can select the active computer automatically, and then operates the display screen as well as peripheral devices. A user thus need not take the trouble to match the display device with the computer to be used.